1. Field of the Invention
The present invention relates to a device which fixes a substrate, and more particularly, to a device, which fixes a substrate for a thin film sputter, having an improved structure so as to uniformly deposit thin films on the substrate, and a method of fixing the substrate using the same.
2. Description of the Related Art
Organic electroluminesence displays are spontaneous luminescence type displays, which electrically excite a fluorescent organic compound to emit light. The organic electroluminesence displays have advantages in that they can be driven at a low voltage and manufactured with a narrow thickness. The organic electroluminesence displays are viewed by many as next generation displays which can solve many of the disadvantages associated with, for example, liquid crystal displays (LCDs), by having, for example, a wide view angle (WVA) and a fast response time.
Where power is supplied, a current flows with the movement of electrons in the organic electroluminescence displays. In other words, in a cathode, electrons move to a light-emitting layer via the assistance of an electron transport layer, while in an anode, holes move to the light-emitting layer via the assistance of a hole transport layer. The electrons and holes in the light-emitting layer made of an organic material create an exciton having a high energy. Here, a drop in energy of the exciton causes light to be emitted. Light of full color can be realized depending on the kind of an organic material of the light-emitting layer.
Generally, an organic electroluminescence display having the above-described structure is formed by a vacuum deposition method to form organic thin films, such as an electron transport layer, a hole transport layer, a light-emitting layer, or the like. In this vacuum deposition method, a substrate, on which organic thin films will be formed, is mounted inside a vacuum chamber in which a pressure is controlled to be within a range of 10−6–10−7 torr. Next, an organic material contained in a furnace is sublimated so that the organic material is deposited on the substrate. U.S. Pat. Nos. 5,833,823, 6,132,575 and 6,251,233B1 disclose such a vaccum deposition method.
FIGS. 1A and 1B show a portion of a conventional sputter which fixes a substrate so as to form thin films on the substrate. As shown in FIG. 1A, a substrate 11 is mounted over a frame 13. A mask 12, which has predetermined patterns to be formed on the substrate 11, is positioned between the substrate 11 and the frame 13. A fixture 100 is disposed over the substrate 11 to support the substrate 11. The fixture 100 includes a magnet plate 101 and a rubber magnet 102 which is attached onto a backside of the magnet plate 101.
The fixture 100 is positioned over the substrate 11 via a robot carrier (not shown) to support the substrate 11, and the mask 12 is aligned underneath the substrate 11.
As shown in FIG. 1B, the fixture 100 descends to the substrate 11. Then, the mask 12, which is made of a metallic material and is positioned underneath the substrate 11, is deformed toward the fixture 100 having a magnetic force and adheres closely to the substrate 11.
The rubber magnet 102 of the fixture 100 is placed on a back surface of the substrate 11 so as to support the substrate 11. In this manner, where the mask 12 is closely adhered to the substrate 11, a sputtering operation is performed.
However, where a distance between the mask 12 and the fixture 100 is narrow, a central portion of the mask 12 ascends first. In this case, while the central portion of the mask 12 may satisfactorily adhere closely to the substrate 11, both margins of the mask 12 do not properly adhere closely to the substrate 11.
As a result, patterns are not formed in right positions of the substrate 11 and are spread to other portions. Also, where the central portion of the mask 12 ascends prior to other portions of the mask 12, as the mask 12 adheres closely to the substrate 11, the mask 12 slips underneath the substrate 11. Therefore, the substrate 11 may be scratched by the mask 12.
To solve these problems, a conventional fixture 200 shown in FIGS. 2A through 2C has been suggested. The fixture 200 includes a rubber magnet 201 and a mask pressing plate 202 which is adhered onto a lower surface of the rubber magnet 201. A process of fixing the substrate 11 using the fixture 200 will be now described.
First, the fixture 200 is transferred over the substrate 11 via a robot carrier, (not shown) and a mask 12 is aligned underneath the substrate 11. Thereafter, as shown in FIG. 2B, the fixture 200 descends while the mask 12, which is made of a metallic material and is positioned underneath the substrate 11, ascends by a magnetic force of the rubber magnet 201. Here, the mask pressing plate 202 contacts the back surface of the substrate 11.
Next, as shown in FIG. 2C, the mask pressing plate 202 may completely press the substrate 11 so that the mask 12 adheres closely to and is fixed to the substrate 11. Thereafter, a sputtering operation is performed.
However, it is difficult for the mask 12 to completely adhere closely to the substrate 11 since a contact surface of a frame 13 with the mask 12 has the flatness of about 50 micrometers.
Accordingly, in order to improve a close adhesiveness between the substrate 11 and the mask 12, a magnetic force which is stronger than a magnetic force of the rubber magnet 201 has to be used, or a pressing force has to be increased/strengthened. However, where a magnetic body having a magnetic force stronger than the magnetic force of the rubber magnet 201 is used, the mask 12 slips underneath the substrate 11. As a result, an alignment of the mask 12 underneath the substrate 11 may be dislocated, or a leakage current may flow over a completed product. Furthermore, a method of strengthening an adhesive force between the substrate 11 and the mask 12 may crack or scratch the substrate 11.